This invention relates generally to the preparation of samples for analysis and is concerned more particularly with the sample preparation technique known as solid phase extraction (SPE). The invention provides apparatus and techniques for improved sample preparation by solid phase extraction and is especially applicable where very small samples are desired.
Solid phase extraction (SPE) is a sample preparation technique where an analyte of interest is concentrated from a dilute matrix as well as being exchanged into a preferred matrix that is compatible with the analysis process. Typically the analyte is bound to a solid phase support or sorbent, washed and then eluted in a small concentrated volume. Micro Extraction by Packed Sorbent (MEPS™) is a form of micro SPE where the chromatography solid phase (2-3 mg of silica or polymer) is packed into a modified needle of an analytical syringe. In this case, the sample is aspirated onto the solid phase sorbent, commonly called the bed, using the aspirating stroke of the syringe. The solid volume is washed and then the analyte of interest is eluted using a suitable small volume of elution solvent. MEPS is fast, efficient and cost-effective when compared to traditional cartridge-based solid phase extraction. In effect, MEPS integrates the sample preparation and injection into a single device, streamlining workflows as extracts can be introduced directly into the analytical instrumentation.
It is an object of the invention to provide for further improvements in the functionality of MEPS as an advantageous method of solid phase extraction for microsamples.